The 221B from ACST GmbH is a Frequency Multiplier with Input Frequency 250 to 375 GHz, Output Frequency 500 to 750 GHz, Input Power 2 to 10 mW, Output Power -0.9 dBm, Frequnecy 250 to 375 GHz. Tags: Waveguide, Waveguide Multiplier. More details for 221B can be seen below.